1. Field of the Invention
The present invention is generally related to a damping mechanism and, more particularly, to a hydraulically damped mechanism for the steering system of a boat.
2. Description of the Prior Art
Many different types of dampers are known to those skilled in the art. Dampers are typically used to slow the movement of one component in relation to another component. As such, dampers can be used to absorb vibration and other sudden motions.
U.S. Pat. No. 5,257,828, which issued to Miller et al on Nov. 2, 1993, describes a method and apparatus for controlling damping in an electric assist steering system for vehicle yaw rate control. The electric assist steering system comprises a steering torque sensor and an electric assist variable reluctance motor operatively connected to a steering member. A motor control signal is provided in response to a value of the torque signal for control of the assist motor. A motor speed sensor senses speed of the power assist motor and a vehicle speed sensor senses the vehicle speed. A control circuit modifies the motor control signal in response to the sensed motor speed and the sensed vehicle speed signal so as to provide damping that is functionally related to both the motor speed and the vehicle speed for vehicle yaw rate control.
U.S. Pat. No. 4,349,079, which issued to Leiber on Sep. 14, 1982, describes a power steering system for motor vehicles. The system comprises a measurement transducer for the steering direction in close relationship with a piston-cylinder unit which acts simultaneously as the steering damper and as the auxiliary force apparatus. The measurement transducer may also be integrated in the piston of the unit. The control of the hydraulic medium for the piston-cylinder unit takes place preferably via three position valves due to desired throttling in accordance with velocity of the return flow at a particular time.
U.S. Pat. No. 4,736,962, which issued to Motrenec on Apr. 12, 1988, describes a steering stabilizer for vehicles. It is particularly applicable to handlebar controlled vehicles. The stabilizer utilizes a steering column housing having a cylindrical chamber therein. The steering column passes through the actual center of the chamber and hydraulic fluid is held within the chamber. A piston or vane is movable by the turning of the steering column and forces the hydraulic fluid through a restricted passageway whereby the turning of the handlebars is viscously damped.
U.S. Pat. No. 5,052,528, which issued to Sullivan on Oct. 1, 1991, describes a steering knuckle damper. A limited stroke hydraulic actuator which may be located in the structure of a steered axle in a shallow blind bore is disclosed. The piston may be slidably received in the bore and is disposed by an adjustable protrusion secured to the steering system. Displacement of the piston causes hydraulic fluid to flow through an orifice from one side to the other. Resistance to flow of fluid through the orifice damps the motion of the piston and consequently the steering system. A spring returns the piston to an initial position when the steering system is removed from end of travel position.
U.S. Pat. No. 5,603,391, which issued Class et al on Feb. 18, 1997, describes a damper valve for a power steering coupler. The invention relates generally to a damper valve for use on a coupler for hydraulic lines, and, in particular, those which connect a hydraulically actuated servomotor of a servo control to a servo valve. According to the invention, all the elements having a damping effect are arranged captively in the coupler.
U.S. Pat. No. 5,607,035, which issued to Fulks et al on Mar. 4, 1997, describes a hydraulic damper. The damper is intended for use with a motor vehicle and comprises a longitudinally extending tube and a separately formed steering knuckle secured to the tube, wherein the tube is formed from extruded aluminum or aluminum alloy and the steering knuckle is formed from aluminum or aluminum alloy. The steering knuckle includes a tubular portion that overlies and is secured to a portion of the tube through the use of a groove in the tubular portion and a groove in the tube. Adhesive may be injected into the grooves to aid in securing the steering knuckle to the tube.
U.S. Pat. No. 5,184,702, which issued to Schulze et al on Feb. 9, 1993, describes a hydraulic damper. The damper is designed as a piston-cylinder unit. The arrangement has a part forming a vibrational system by means of a spring. Vibrations acting on the damper arrangement are greater attenuated virtually only in the resonant range of the vibrational system because only in this case can vibrations of high amplitude be excited and a high dissipation of energy by way of hydraulic flows in channels and between cylinder chambers takes place.
Newly developed steering systems for boats and other watercraft incorporate electronically controlled signals that eliminate the need for a direct mechanical or hydraulic connection between a steering wheel or other manually movable steering mechanism and the control surfaces which actually implement the steering command. For example, in an electrically controlled boat system incorporating either an outboard motor or a sterndrive, movement of a steering wheel by an operator can create electronic signals that result in the appropriate steering movement of the outboard motor or sterndrive, but the steering wheel is not directly connected to the outboard motor or sterndrive either hydraulically or mechanically. As a result, the operator feels virtually no resistance when the steering wheel is moved. In these types of steering systems, which are commonly referred to as "steer by wire" systems, the lack of feel or resistance in the steering wheel can lead to potentially dangerous circumstances. It would therefore be significantly beneficial if the steering mechanism of a boat or watercraft could be provided with a system that resists an operator's movement of the steering wheel in a manner that is similar to the natural resistance experienced by the operator of a boat or watercraft when a mechanical or hydraulic steering system is used.